I use
Wireshark. The test procedure is simple; just call a Voxalot number and observe the Source and Destination IP addresses of the
RTP (voice) packets. This issue is important because RTP packets sent through a proxy can be delayed or dropped, causing poor audio quality.
Many Voxalot users assume the RTP packets always take the most direct route through the Internet. This is not always the case, particularly when calling out through one of the Betamax companies, that's been my experience. I have also seen the Voxalot proxy handling RTP packets when I place a call to a Voxalot user who's ATA is behind a router and has mis-configured NAT settings.